1. Technical Field
This invention relates to multi-part fastener assemblies having vibration isolating features. Such fasteners are used, for example, to secure a valve or rocker arm cover of an engine to the cylinder head while preventing vibration from being transmitted through the fastener from one component to the other (e.g. from the cylinder head to the valve cover or body).
2. Related Prior Art
Multi-part fastener assemblies are well known for attaching two components, such as a valve or rocker arm cover to a cylinder head in a manner that prevents vibration from being transmitted through the fastener from one of the components to the other. U.S. Pat. No. 4,975,008 shows the general construction of such fasteners, wherein a captive sleeve is disposed about the threaded shank of a bolt, confronting the head of the bolt at its upper end and the cylinder head at its lower end to limit the torque of the bolt when tightened. A resilient grommet is carried about the sleeve and, as illustrated, is received in a cup-shaped well provided in the cylinder head or, in this case, a rocker arm cover. As the bolt is tightened, the grommet is compressed and is deformed and contained within the well of the clamped member. The grommet serves to isolate the bolt from the rocker arm cover as well as to seal the access opening for the bolt.
Fasteners of the above general type are satisfactory in applications where there is sufficient support for the grommet (i.e., enough space to provide a cup-shaped well into which the grommet is received). As engines become smaller and more compact and the available space for the various components of the engine becomes less and less, there likely will be some applications in which the space required to provide the needed grommet well is not available or, if available, could be better used by other engine components.
It would thus be desirable to provide a vibration isolating fastener assembly that does not require support by a grommet well of the clamped component, such as a valve or rocker arm cover.